Instructions

Make the Meat Filling.

Add the oil to a large skillet and place it over
medium-high heat for 2 minutes. Add the onions. Cook 5 minutes, stirring
occasionally.

Add the ground beef (or ground lamb) to the
skillet and break it apart with a wooden spoon. Add the parsley, rosemary,
thyme, salt, and and pepper. Stir well. Cook for 6-8 minutes, until the meat is
browned, stirring occasionally.

Add the Worcestershire sauce and garlic. Stir to
combine. Cook for 1 minute.

Add the flour and tomato paste. Stir until well
incorporated and no clumps of tomato paste remain.

Add the broth, frozen peas and carrots, and
frozen corn. Bring the liquid to a boil then reduce to simmer. Simmer for 5
minutes, stirring occasionally.

Set the meat mixture aside. Preheat oven to 400
degrees F.

Make the potato topping.

Place the potatoes in a large pot. Cover the
potatoes with water. Bring the water to a boil. Reduce to a simmer. Cook until
potatoes are fork tender, 10-15 minutes.

Drain the potatoes in a colander. Return the
potatoes to the hot pot. Let the potatoes rest in the hot pot for 1 minute to
evaporate any remaining liquid.

Add butter, half & half, garlic powder,
salt, and pepper. Mash the potatoes and stir until all the ingredients are
mixed together.

Add the parmesan cheese to the potatoes. Stir
until well combined.

Assemble the casserole.

Pour the meat mixture into a 9×9 (or 7×11) inch
baking dish. Spread it out into an even layer. Spoon the mashed potatoes on top
of the meat. Carefully spread into an even layer.

If the baking dish looks very full, place it on
a rimmed baking sheet so that the filling doesn’t bubble over into your oven.
Bake uncovered for 25-30 minutes. Cool for 15 minutes before serving.